There is substantial evidence supporting the existence of a complex, bi-directional link between the CNS and immune system. Both opioids and the neuropeptide substance P (SP) play important roles as a modulator of neuroimmuno-regulation and are involved in modulation of the CNS and immune system. The goal of this project is to address our overarching hypothesis that the interactions between opioids (e.g., morphine) and SP have a cofactor role in the immunopathogenesis of HIV-1 disease and neuroAIDS. We propose a series of in vitro, ex vivo and in vivo studies (Aims 1, 2 and 3) to examine the role of opioids and/or SP in suppression of host innate immunity against HIV-1 infection in both immune and neuronal systems. We will focus on the impact of opioids and/or SP on type 1 IFN- and APOBEC3G/3F (newly identified ant-HIV factors)-mediated innate immunity against HIV-1, as these cellular factors are the key elements of anti-HIV host-defense mechanism. We also will illustrate the in vivo implications of opioid-mediated alterations of type 1 IFN-1/2 and APOBEC3G/3F expression using the specimens (PBMC and brain tissues) obtained from opioid-dependent and non-opioid-using subjects with HIV-associated neurocognitive impairment. We propose the following specific aims to address previously unrecognized mechanisms by which opioids and /or SP compromise IFN/APOBEC-mediated innate immunity, increasing the susceptibility of immune and the CNS cells to HIV-1 infection and injury. In aim 1, we will examine whether opioids and/or SP impair type 1 IFN/APOBEC-mediated innate immunity against HIV-1 infection of the immune cells, CD4+ T cells and macrophages, the primary target in the peripheral blood for HIV-1 infection; In aim 2, we will determine whether morphine and/or SP impair type 1 IFN and APOBEC-mediated innate immunity in the CNS cells: microglia, astrocytes and neurons; In aim 3, we will examine the in vivo impact of opioid use and/or HIV on the expression of type 1 IFN-1/2 and APOBEC3G/3F in the CNS. We will examine the mRNA levels and the localization of protein expression of type 1 IFN-1/2 and APOBEC3G/3F in the brain specimens from opioid-dependent and non-opioid using subjects with HIV-associated neurocognitive impairment. The proposed studies, if successful, will contribute to a better understanding of the role of opioids and/or SP in the impairment of specific and critical innate immune defense mechanism in both immune and neuronal systems. Our studies also will facilitate a rational basis for practical guidance towards the reduction of risk factors, such as heroin, that may potentiate HIV-1 infection and promote the development and progression of neuroAIDS.